1. Field of the Invention
This invention relates in general to magnetic heads and, in particular, to an improved form of magnetoresistive (MR) head.
2. Description Relative to the Prior Art
For a variety of reasons, there is--in the magnetic recording arts--a trend toward the use of multitrack magnetic heads having a large number of gapped transducer cores per widthwise inch of such heads. Typically, core-to-core spacing may be on the order of 6 mils. In order to build a head with a large number of cores per widthwise inch thereof, photolithographically shaped thin films are often employed for individual core structures. Whereas a record head may be effective while employing a minimal number of coil turns per core leg, a reproduce head on the other hand will often require a relatively large number of turns--typically 200--per core leg. Reason: while large currents can be applied to a record head with few turns to effect signal recording, a large number of coil turns coupled to a reproduce head is necessary to develop a signal from the relatively weak flux associated with recorded signals. Coil structures, like core structures, are formed of deposited thin films.
Given the tight spacing between adjacent cores of a high density multitrack head, an impasse occurs as more and more coil turns are crammed into coupled cooperation with the core legs. Imagine, for example, the task of depositing a 200-turn thin film coil within a 6 mil spacing. To address this problem, those in the art have drifted toward the use of coil-less MR elements to sense recorded signal flux. As is known, an MR element varies its electrical resistance in response to applied magnetic flux; and so, when a sense current is applied to an MR element, such current will vary in proportion to--and as the analog of--the recorded signal flux.
To maximize the response of a thin film head core having an MR flux sensing element, it is usually desirable to situate the MR element as close to the medium-contacting surface of the core as is possible, whereby the full impact of recorded signal flux will be felt directly by the MR element. So locating an MR element, however, is not without difficulty: the closer the MR element is to a recording medium with which it cooperates, the more the MR element will be subject to noise associated with thermomechanical interaction between the core and medium . . . which interaction magnetostrictively affects the MR element. While it is, of course, possible to configure core parts so as to position an MR element far from the medium-contacting surface of the core to obviate the noise problem, such a tack is self-defeating in that it inherently builds inefficiency into the head as the flux leakage path is increased.
Representative prior art patents depicting MR heads of the type that directly responds to recorded signal flux are: U.S. Pat. Nos. 3,860,965, 3,864,751, 3,987,485, 4,012,781, 4,255,772, and 4,375,657.